A yellow alert was issued by the Beijing Meteorological Bureau on Oct. 18, following the arrival of heavy smog. With visibility of less than 500 meters in some areas, certain Beijing landmarks could not even be seen with the naked eye.

Until 4 p.m. on Oct. 19, the density of fine particulate matter PM2.5 in Beijing's six downtown districts surpassed 150 micrograms per cubic meter, and the air pollution reached a Level 5. The air quality index in Beijing was 225 on the morning of Oct. 19, indicating severe air pollution.

Local landmarks, such as CCTV headquarters, were almost entirely obscured by fog. The poor visibility also caused traffic to move slowly, and many citizens chose to wear masks while doing outdoor activities.